1. Field of the Invention
The invention relates to high-powered antenna installations employable in rotatable electrical systems for the transmission and reception of electromagnetic energy and, more particularly, relates to an integral radome-antenna structure which is mounted for rotation on the exterior of an aircraft.
The utilization of integral radome-antenna structures, and particularly such types of structures which are rotatably mounted on aircraft and employed as so-called airborne early warning systems (AEW) is well-known in the technology, and has successfully found widespread applications in conjunction with military surveillance aircraft,, especially aircraft adapted to be launched from naval carriers. In various instances, as currently utilized in military aircraft, such radome-antenna structures are mounted positions so as to be superimposed above the fuselage of the aircraft, although conceivably also being suspendable from below the fuselage, and incorporate a depending shaft structure, generally hollow in nature, extending downwardly from the radome into the fuselage of the aircraft, and wherein the shaft is operatively connected to a suitable drive arrangement for simultaneously rotating the shaft about the longitudinal axis thereof and the radome-antenna structure at specified speeds of rotation. Suitable couplings and slip ring assemblies may be provided in order to connect the antenna array contained in the radome to suitable stationary sources of electrical energy while, concurrently, enabling the pick-up of signals received by the antenna array and to transmit the signals to stationary signal processing component and/or display consoles which are located in the cabin of the aircraft. Moreover, a suitable cooling fluid may also be transmitted to the antenna components contained in the radome through the intermediary of the hollow shaft mounting and supporting the radome-antenna installation for rotation. However, the components for supplying electrical energy to the antenna array and picking up the signals derived therefrom, in addition to the heat exchange structure for circulation of a cooling fluid for the rotating components of the radome-antenna structure are normally stationary components mounted in the interior of the aircraft. Although this is generally adequate and satisfactory for utilization with currently employed low or moderately powered airborne radome-antenna surveillance systems, which generally employ complex rotary couplings to transfer electrical power and/or radio frequency signals between the revolving radome and the stationary equipment contained in the aircraft, the development of much more sophisticated and higher-powered surveillance systems, particularly of the airborne radome type, has rendered the use of such rotary couplings for the transfer of electrical power and signals between rotating and stationary components to be extremely inefficient in view of significant and frequently untenable electrical losses ordinarily encountered with the rotary couplings which are currently designed in such radome installations. High-powered systems of this type which are presently being contemplated for installation in airborne rotatable radome-antenna structures may necessitate the generating and distribution of electrical power at a level which is a multiple of that in presently utilized systems, and may conceivably incorporate an excess of fifty or even more separately controllable electrical circuits within the rotatable radome. Such electrical circuits must be able to be accommodated in the rotary coupling, and hence signifies a greater potential for encountering electrical losses and signal distortions in the radio frequency signals which are received from the antenna array contained in the radome.
In order to reduce the potential for considerable electrical losses and signal distortion in such high-powered systems which are contemplated in utilization with the rotatable radome-antenna structure pursuant to the invention, there is accordingly proposed the use of a rotating equipment rack which is arranged interiorly of the aircraft fuselage, such as within the cabin space of the aircraft, and which is rigidly fastened to and concurrently rotatable with the rotating shaft supporting the radome-antenna installation for rotation, so as to constitute essentially a unitary assembly therewith. This enables that practically all of the surveillance system equipment be contained in the radome; in essence, the antenna array and associated electrical and signal receiving components, and the rotating equipment rack supporting surveillance system components mounted on the rotatable shaft may be permanently or hard-wired together so as to impart a greater degree of efficiency and resultingly reduced power losses and signal distortion to the system. In conjunction therewith, the electrical power which is to be generated for the surveillance system components in the radome and on the equipment rack is supplied through the intermediary of electrical generators, which are driven or powered by an air turbine motor fixedly fastened to and suspended from a shelf mounted on the lower end portion of the rotatable shaft at a location below the floor of the crew cabin of the aircraft; and which rotates with the shaft.
The novel and unique connection of the electrical components which are mounted on the equipment rack which is fastened to and rotatable in unison with the shaft supporting the radome-antenna structure, enables the restriction to or positioning of all of the high-power RF and other analog signal generating and processing components to the inventive rotating equipment rack and radome, with the electrical power generation, analog beam forming, signal processing and analog/digital conversion taking place in the components supported on the hard-wired rotating assembly supported on the equipment rack interiorly of the aircraft.
Moreover, the air turbine motor which is mounted on the shelf fastened to the lower end portion of the rotatable shaft below the cabin floor of the aircraft, and which is powered by aircraft bleed air, is adapted to drive and power one or more electrical power generators, which are also supported from the shelf, for supplying electrical power to the surveillance system components contained in the radome or mounted on the equipment rack. Hereby, a multi-function rotary coupling is mounted on the bottom end portion of the hollow rotatable shaft, and is supported from the aircraft fuselage structure, so as to enable aircraft bleed air to be supplied to the air turbine motor which is suspended from the rotatable shelf, while enabling the supply therethrough into suitable conduits in the shaft for the circulation of a cold liquid coolant to all equipment in the radome and on the rotating equipment rack requiring positive or forced cooling thereof, and enabling receipt of hot liquid coolant return flow for discharge from the rotating installation for subsequent transfer to a stationary internal heat exchanger, the latter of which may be mounted at a suitable location in the aircraft, such as below the cabin space thereof in attachment to the fuselage.
2. Discussion of the Prior Art
Although various rotatable radome-antenna structures which are mounted on aircraft are currently in widespread application, particularly radomes supported on or from military surveillance radar aircraft, none of these disclose the mounting of the major electrical components and equipment on the rotating structure of the system, so as to inhibit or, in any event, considerably reduce the unacceptable levels of power losses or extent of signal distorting which may be encountered with regard to contemplated high-powered airborne radome surveillance systems.
Colman et al., U.S. Pat. No. 3,045,236, discloses a rotatable radome-antenna assembly which is mounted on an aircraft, and in which the assembly is supported on a rotatable hollow shaft extending downwardly through the aircraft fuselage. The lower end of the shaft includes a coupling for connection to a cooling unit and to a source of power for the electronic system components contained in the radome; whereas the upper portion of the hollow shaft within the fuselage incorporates a drive motor geared to the periphery of the shaft for imparting a predetermined rotational movement to the radome-antenna assembly. Although this type of structural and operational system would appear to be adequate for the relatively low electrical power requirements of currently employed rotating radomes, the high level of power losses and signal distortion encountered through the use of such structure for high-powered airborne surveillance systems as contemplated by the present invention would be unacceptable in the technology.
Davis, U.S. Pat. No. 3,026,516, discloses a rotatable radome for use on aircraft, wherein the rotatable radome is mounted on a heavy pylon which is fastened to the upper surface structure of the aircraft fuselage. Herein, there is also no disclosure of the various electronic and signal processing components and drive arrangements including the cooling conduits for the system being mounted so as to be rotatable in conjunction with the radome-antenna structure, thus potentially resulting in considerable energy losses when intended to be employed in connection with a high-powered surveillance system necessitating the installation of a greater complexity and quantity of sophisticated electronic and mechanical devices.
Clanton, Jr. et al., U.S. Pat. No. 2,980,909, disclose a radome-antenna installation which is mounted for rotation on a pylon fastened to the empennage section of an aircraft. In essence, this would be subject to the same limitations and drawbacks as in the construction of Davis U.S. Pat. No. 3,026,516. Basically, the structure disclosed in this patent would not be conducive towards affording a reduction in losses of electrical power and signal distortion to a level which would be acceptable in the higher-powered systems contemplated by the present invention for sophisticated and advanced military surveillance and early warning aircraft of this type.